@Marty ********
Theoretically, if a prenup were written in Thailand AND it were written in accordance with all applicable U.S. laws, then sure, it would be enforceable in the U.S.. However, finding a Thai (or even American lawyer in Thailand) intimately familiar with all the variations in the law in different states is unlikely. That's why lawyers need to pass the bar in different states. If he feels comfortable with a Thai lawyer with expertise in the applicable state, sure, he can go for it. It wouldn't be the approach I would take.